Vulnerability assessment of drinking water treatment plants

In the aftermath of an earthquake it is essential that drinking Water Treatment Plant (WTP) and the relative distribution network keep their full, or at least, partial functionality. Indeed, a complete failure of such systems, associated to a long restoration time can result in serious damages to facilities and services depending on water supply as well as harmful consequences for the population. Actually, a WTP shutdown can amplify the damages caused by an earthquake in terms of economical and human losses by failing the supply of fire fighting network and consequently the extinguishment of potential fires, as well as getting worse the hygienic and sanitary conditions of population affected by the natural events, thus favouring the outbreaks of epidemics as it happened in Haiti, where cholera killed hundreds of thousands of people after the earthquake of January 12th, 2010. This paper deals with the assessment of seismic vulnerability of WTPs that constitute the first element of the water distribution network by analyzing the effects of past earthquakes on them with the aim of determining the main causes of damage (ground failure, sloshing phenomenon, structural weakness, etc') as well as the weaker elements and then, on the base of risk analysis theory, drawing fragility curves that can be useful tools for designing reliable new WTPs and controlling the resilience of those already in service

Experimental study for the reduction of CO2emissions in wastewater treatment plant using microalgal cultivation

Wastewater treatment plants (WWTPs) contribute to CO2 emissions in atmosphere through direct (biological metabolism) and indirect (fuel combustion) oxidation of organic carbon. This detrimental effect of WWTPs operation can be mitigated by integrating the traditional treatment with a microalgae cultivation pond where CO2 is fixed into autotrophic biomass and the positive side effect of removing nutrients also takes place. To test the feasibility of this modified WWTPs configuration, a pilot-scale 200 L raceway pond, operating outdoor, was designed and used for biomass cultivation in untreated urban wastewater. Nitrogen gas enriched with 20% CO2, simulating the exhausted gas of biogas combustion, was supplied continuously during daytime at different flowrates. The dynamics of microalgae growth as well as inorganic carbon and nutrients uptake were studied during the pond start-up and semi-continuous feeding conditions. The absorbed bio-available CO2 was monitored during daylight for different gas flowrates (0.2, 0.4 and 1.0 L/min) and for wastewater semi-continuous feeding conditions (0.8 L/h). The highest efficiency, equal to 83%, of bio-available CO2 fixation was obtained for the lowest gas flowrate of 0.2 L/min., whereas the highest CO2 removal rate of 24.6 mg/L/min was reached for the highest gas flowrate of 1.0 L/min. Furthermore, this operating condition resulted in the highest microalgae biomass productivity of 28.3 g/d/m2. Nutrients removal was complete for each operating condition tested

Experimental study for the reduction of CO2 emissions in wastewater treatment plant using microalgal cultivation

Wastewater treatment plants (WWTPs) contribute to CO2 emissions in atmosphere through direct (biological metabolism) and indirect (fuel combustion) oxidation of organic carbon. This detrimental effect of WWTPs operation can be mitigated by integrating the traditional treatment with a microalgae cultivation pond where CO2 is fixed into autotrophic biomass and the positive side effect of removing nutrients also takes place. To test the feasibility of this modified WWTPs configuration, a pilot-scale 200 L raceway pond, operating outdoor, was designed and used for biomass cultivation in untreated urban wastewater. Nitrogen gas enriched with 20% CO2, simulating the exhausted gas of biogas combustion, was supplied continuously during daytime at different flowrates. The dynamics of microalgae growth as well as inorganic carbon and nutrients uptake were studied during the pond start-up and semi-continuous feeding conditions. The absorbed bio-available CO2 was monitored during daylight for different gas flowrates (0.2, 0.4 and 1.0 L/min) and for wastewater semi-continuous feeding conditions (0.8 L/h). The highest efficiency, equal to 83%, of bio-available CO2 fixation was obtained for the lowest gas flowrate of 0.2 L/min., whereas the highest CO2 removal rate of 24.6 mg/L/min was reached for the highest gas flowrate of 1.0 L/min. Furthermore, this operating condition resulted in the highest microalgae biomass productivity of 28.3 g/d/m2. Nutrients removal was complete for each operating condition tested

Vulnerability Assessment of Drinking Water Treatment Plants

In the aftermath of an earthquake it is essential that drinking Water Treatment Plant (WTP) and the relative distribution network keep their full, or at least, partial functionality. Indeed, a complete failure of such systems, associated to a long restoration time can result in serious damages to facilities and services depending on water supply as well as harmful consequences for the population. Actually, a WTP shutdown can amplify the damages caused by an earthquake in terms of economical and human losses by failing the supply of fire fighting network and consequently the extinguishment of potential fires, as well as getting worse the hygienic and sanitary conditions of population affected by the natural events, thus favouring the outbreaks of epidemics as it happened in Haiti, where cholera killed hundreds of thousands of people after the earthquake of January 12th, 2010. This paper deals with the assessment of seismic vulnerability of WTPs that constitute the first element of the water distribution network by analyzing the effects of past earthquakes on them with the aim of determining the main causes of damage (ground failure, sloshing phenomenon, structural weakness, etc…) as well as the weaker elements and then, on the base of risk analysis theory, drawing fragility curves that can be useful tools for designing reliable new WTPs and controlling the resilience of those already in service

Effect of light intensity and nutrients supply on microalgae cultivated in urban wastewater: Biomass production, lipids accumulation and settleability characteristics

Microalgae cultivation systems fed with wastewater as source of nutrients represents the principal sustainable condition to produce microalgal biomass to be converted conveniently to biofuels. In order to optimize microalgae growth and their lipid content, the effect of light intensity and nutrients load in real wastewater was investigated through batch microalgal cultivation tests. A microalgal polyculture was used as inoculum and grown for 10 days in batch at different conditions of light intensity (i.e. 20, 50 and 100 μmol s−1m−2) and nutrients concentration in wastewater. Experimental results showed that biomass productivity decreased for rich nutrients conditions and increased for high light intensities. The highest lipid mass content (29%) was found for high light intensity condition (100 μmol s−1m−2). Furthermore, microalgae settleability tests, conducted at the end of the cultivation time, resulted in the highest biomass recovery efficiency (72%) for low light intensity and nutrients supply conditions

Effect of light intensity and nutrients supply on microalgae cultivated in urban wastewater: Biomass production, lipids accumulation and settleability characteristics

Microalgae cultivation systems fed with wastewater as source of nutrients represents the principal sustainable condition to produce microalgal biomass to be converted conveniently to biofuels. In order to optimize microalgae growth and their lipid content, the effect of light intensity and nutrients load in real wastewater was investigated through batch microalgal cultivation tests. A microalgal polyculture was used as inoculum and grown for 10 days in batch at different conditions of light intensity (i.e. 20, 50 and 100 μmol s−1m−2) and nutrients concentration in wastewater. Experimental results showed that biomass productivity decreased for rich nutrients conditions and increased for high light intensities. The highest lipid mass content (29%) was found for high light intensity condition (100 μmol s−1m−2). Furthermore, microalgae settleability tests, conducted at the end of the cultivation time, resulted in the highest biomass recovery efficiency (72%) for low light intensity and nutrients supply conditions

Methane production from anaerobic co-digestion of orange peel waste and organic fraction of municipal solid waste in batch and semi-continuous reactors

A large amount of orange peel waste (OPW) is yearly generated due to the high production of oranges all over the world. A high percentage of this waste is dumped every year without any proper treatment, thus causing environmental issues as a consequence of dispersion of biological degradation by-products (i.e. biogas and leachate) into the environment. An effective, suitable and environmentally friendly treatment for OPW is therefore required. Biogas production under controlled conditions by an anaerobic digestion (AD) process is highly recommendable and it has been demonstrated to be potentially high efficient when OPW is used as substrate. However, the high content of essential oils, mainly composed of limonene, a well-known antioxidant, can cause the inhibition of the biological activity. A low limonene concentration inside the anaerobic digester can be effective to avoid this inhibition. Therefore, anaerobic co-digestion of OPW with organic fraction of municipal solid waste (OFMSW) was carried out in order to reduce limonene concentration, by dilution, in the organic mixture. Three different mass ratios of the two substrates (i.e. 1:3, 2:2, 3:1) were considered (each of them with different limonene concentrations) and used in two separate experiments: batch and semi continuous. The content of limonene inside the digester is directly related to the organic loading rate (OLR). The maximum OLR that resulted in stable anaerobic co-digestion process performance was 2 gVS(L−1·day−1) corresponding to 26.7 mgLimonene(Ldigester−1·day−1) of limonene dosage. The highest methane production obtained from such an OLR was around 0.70 ± 0.05 LCH4(Ldigester−1·day−1)

Insights into bioflocculation of filamentous cyanobacteria, microalgae and their mixture for a low-cost biomass harvesting system

Cyanobacteria and microalgae are considered as interesting feedstocks for either the production of high value bio-based compounds and biofuels or wastewater treatment. Nevertheless, the high costs of production, mainly due to the harvesting process, hamper a wide commercialization of industrial cyanobacteria and microalgae based products. Recent studies have found in autoflocculation and bioflocculation promising spontaneous processes for a low-cost and environmentally sustainable cyanobacteria and microalgae biomass harvesting process. In the present work, bioflocculation process has been studied for three different inocula: filamentous cyanobacteria, microalgae and their mixture. Their cultivation has been conducted in batch mode using two different cultivation media: synthetic aqueous solution and urban wastewater. The removal of nutrients and flocculation process performance were monitored during the entire cultivation time. Results have proved that bioflocculation and sedimentation processes occur efficiently for filamentous cyanobacteria cultivated in synthetic aqueous solution, whereas such processes are less efficient in urban wastewater due to the specific characteristics of this medium that prevent bioflocculation to occur. Besides different efficiencies associated to cultivation media, this work highlighted that bioflocculation of sole microalgae is not as effective as when they are cultivated together with filamentous cyanobacteria